Invasive Exotic Species - Essay Example

Invasive Exotic Species Gypsy Moth: An Analytical Paper Contents of the Report Introduction Exotic Invasive Species The Gypsy Moth Gypsy Moth: The Environmental Impacts Steps to Combat the Gypsy Moth Invasion Conclusion Introduction Our Earth is home for more than 30 million species of insects. This clearly indicates that it is important to know the interactions of living beings with nature and its impact on human beings. (Triplehorn, 2005) Entomology is a Greek word formed with the combination of entamo meaning insects and logy meaning study. Hence, Entomology is a branch of zoology that deals with the study of insects. (Triplehorn, 2005) As the interaction of this species with nature and human beings is more, it forms an important aspect in biology. The scientific study of insects has its beginning as early as the sixteenth century. Entomologists classify insects based on their taxonomy into various groups known as apiology, coleopterology, dipterology, heteropterology, lepidoptrelogy, myrmecology, orthopetrology, trichoptrology (Triplehorn, 2005) Each entomologist spends his life in the study of any one of these groups. Insect identification is very difficult as the attributes distinguishing them are often invisible or unclear. The Exotic Species (Invasive species) Exotic species are defined as those organisms that are not specific or intrinsic to a particular area. (Naylor, 2001) Their origin is a different place than their place of living. Scientific study and results prove that some introduced species are a threat to the ecosystem in which they get transferred. More scientifically, Introduced species are "species that have become able to survive and reproduce outside the habitats they evolved or spread naturally" (Naylor, 2001). Species are introduced in a habitat usually while they are transported from one region to another. These introductions can be accidental or intentional. Intentional inductions by humans is done thinking that a certain group of species is some how beneficial to human beings. Invasive species are one sub group of introduced species that have an ill effect on their foreign ecosystem. They behave as pests (G. K. Meffe. 1998). These immigrants breed expand and develop at an exponential pace causing great damage to the eco relations. Its effect is simply defined in three terms namely arrive, survive and thrive. There are many clauses for a species to become invasive. It has to find a suitable vector to transfer it from its habitat to another one. The climatic conditions of the new habitat must match closely with its previous habitat. It should be capable to survive in that habitat and also outperform the existing native species and has to start spreading throughout like a plague. (Townsend CR. 1991) Basically invasive species have a negative impact on the new ecosystem. Some of the characteristics for an invasive species are the mode of reproduction, Asexual as well as sexual reproduction, the ability to withstand a wide range of climatic conditions and the reproductive output. (Townsend CR. 1991) One of these species that is responsible for defoliation of trees is the Gypsy Moth. The Gypsy Moth The scientific name of gypsy moth is Lymantria dispar. It is commonly called as gypsy moth to symbolize its mobility, that is, the pace at which it covers an area and also European moth. It is of the order Lepidoptera, class insecta and phylum Arthropod. This moth has its origin basically from Europe, Asia and North Africa. (ent.msu.edu, 1997) The Gypsy Moth This moth has been introduced in the North America and East Coast in the year 1869. It was an intentional introduction of this moth. A French scientist named Lepold Trovelot who lived in Massachusetts has introduced this moth. He was experimenting different moths and silk worms for having better quality silk production (Forbush, 1896). He with the intension of breeding silk worms with other moths introduced the gypsy moth in North America. His experiment failed. Some of the moths brought by him escaped into the new habitat. They found that the new place was suitable for their dwelling. The gypsy moth happens to be one of the notorious pests in North America after this incident. This moth happens to be one of the most hated insects in the US. The US government is making their best efforts, flooding money in order to extricate them. However their spread across the region is alarmingly increasing. Gypsy moth affects the forest cover in any area by defoliation of trees. Gypsy moth makes its life in four distinctive phases, with a generation every year (Gerardi, 1979). The first phase is of the egg masses. The female lays eggs in any sheltered region, branches and trunks of trees. They are even known to fly to ships and laying their eggs over there. The next stage is of the larvae. The larva will be developed four to six weeks to the time the eggs are laid. The success rate of survival of this moth lies in the fact that the eggs can withstand to extreme climatic conditions, that is, either freezing levels or extreme hot climates (Gerardi, 1979). The egg masses will bleach out due to sun rays. The female after laying eggs leaves a hair like structure around the eggs from her abdomen. This is a kind of protection for the eggs. Egg masses will be generally large in number. They range from two's of hundreds to thousands. The larvae phase of the moth coincides with the early spring, the time when most hardwood trees would start budding. Either the larvae are transmitted through wind to different places or artificial transportation of larvae takes place. The larvae phase consists of multiple molts in which the larva increases in size. The Larvae stage The intermediary phases in the molts are known as instars (Gerardi, 1979). A male undergoes five instars and the female has six in star phases. In the beginning the larva grows on the leaves of the trees feeding on the holes of the leaves. In Later phases it feeds on from outer half of the leaf to its center. The larva tends to be active at nights and rest in the day. The feeding on a tree is done until the foliage on that tree is completely done. The search for new food sources turns on later. After this stage the larva changes to the pupa form that takes around two weeks for incarnation (Gerardi, 1979). The Young Gypsy moth Caterpillar This is the time when they change into Moths. The female moth generates pheromone that attracts males and contributes for their multiplicity. Both the adult moths die once the female lays eggs. Gypsy moths are diurnal and most are active after dusk or later at night. Gypsy Moth: The Environmental Impacts Gypsy moth basically feeds on oaks, aspen, apple, paper birch, willows, ash trees, catalpa, balam fir and the list goes on and on and on. They almost feed on over 600 species of trees (Gerardi, 1979). One of the major effects of gypsy moth is the defoliation of trees. Defoliation of trees is based on three factors namely the condition of tree when defoliated, total number of defoliations and the availability of soil moisture. The effect on the tree is based on the fifty percent index (Liebhold, 1992). If the defoliation is less than fifty percent the there would be a slight reduction in growth of the tree. If the defoliation rate is more than fifty percent and the tree is already defoliated then the tree dies out else it refoliates and weakens in its strength. Further defoliations may result in the dying out of the tree. About 30-50 % of growth reductions are seen in defoliated trees. Defoliated trees are prone to attack by many other organisms like the fungi. The tree dies out 2-3 years after the defoliation activity. (Liebhold, 1992) Defoliation of Hardwood Apart from the hardwood trees, pine and hemlocks are also affected by this activity. A study says that about 50% of pines and 90% of hemlocks will be killed in the first defoliation. The gypsy moth had greatly influenced the forests in US. From 1980's it defoliated around 4,000 square kilometers of forest area every year. It reached a record clearance of 52,200 square kilometers in 1981 (Liebhold, 1992). Annual loss due to this moth for the US has been around 30 Million dollars. After this tragic incident the Government of US has decided to spend around 200 Million dollars annually to prevent the spread of this moth. Since 1869, the spread rate of this moth has been twenty one kilometers annually (Liebhold, 1992). During an outbreak in US around 16 Million acres of hardwood was defoliated. Loss to the state of Pennsylvania alone was around 72 Million Dollars and from 1968 to 1985 around 219 Million Dollars was the loss to state (Liebhold, 1992). An amount of 30 Million Dollars every year is spent for its eradication. Among the other infected areas is Michigan due to its vast dense forest regions. Steps to Combat the Gypsy Moth Invasion There are tolerable levels of this moth and a variety of methods can be followed in order to keep the number under tolerable level. Some of the methods are continuous monitoring of the Gypsy moth population and killing the larvae using insecticides and hence maintaining the health levels of trees high. Gypsy moth traps can be used to attract the moths and they can be killed (Gould, 1990). In the case of an outbreak use of bacterial pesticides could be very helpful. Maintaining a considerable health level for the trees by having proper planning while plantation, seeing that the neighborhood trees do not compete for nutrients and moisture, fertilizing shade trees, avoiding applying lime or weed killers around trees that degrade the health of the trees etc can be done. Other mechanisms include the control of Gypsy moth in the biological way that is, using their predators to kill them. The technid flies, braconid wasps and soldier beetles (Gould, 1990) are some of their predators that can be purchased commercially or attracted by using supporting trees and can be used for killing Gypsy Moth. However the solution of including pesticides include many factors like the percentage of defoliation, number of dead trees and the neighborhood threat of the moth etc (Gould, 1990). If the Gypsy moth larvae or eggs are highly dense then going for pesticides would be a better solution. Usage of microbial and biological pesticides like Nucleopolyhedros virus (NPV) that is, GypChek or bacillus thuringiensis (BI) is effective over the chemical pesticides that contain poisons (Gould, 1990). Some of the commonly used pesticides are Malathion, diflubenzunon and trichlorfon. Another approach is using the Thinning process of silviculture in which surplus trees in forests are cut in order to eliminate the problems from moths like this (Nyland, 2002). Apart from that other methods like removal of eggs from trees and burning them. Usage of gum like substances on the trees to prevent the crawling of moths can be done. Conclusion Gypsy moth has caused a lot of damage in the North American region. The defoliation of trees is a major problem and should be treated on War foot basis. Funds should be flooded by government in order to prevent the further immigration of the moths from external habitats. Usage of biological techniques in order to eliminate the Gypsy moth propagation including the usage of bacterial and microbial pesticides will be helpful. Practices such as Thinning will eliminate much of the favorable hotspots for moth dwelling. Usage of artificial insecticides may cause harm to other living beings that are useful to the habitat. Hence, their use should be discouraged. Preventive measures are always better than finding a temporary solution. Maintaining the tolerable level of moths by constantly monitoring their population and providing funds to research on the possible ways of eliminating this problem should be encouraged. References 1. Triplehorn, Charles A. and Norman F. Johnson (2005-05-19). Borror and DeLong's Introduction to the Study of Insects 2. Naylor, R.L., S.L. Williams, and D.R. Strong. 2001. Aquaculture-A gateway for exotic species. 3. Burdick, Alan. 2005. Out of Eden: An Odyssey of Ecological Invasion. Farrar Straus and Giroux. 336 p. ISBN 0-374-21973-7 4. Williams, J.D. and G. K. Meffe. 1998. Nonindigenous Species. In: Status and Trends of the Nation's Biological Resources. 5. Townsend CR. 1991. Exotic Species Management and the Need for a Theory of Invasion Ecology. 6. Doane, C. C. and McManus, M. L., editors. 1981. The Gypsy Moth: Research toward Integrated Pest Management. U. S. Department of Agiculture Forest Service Science and Education Agency, Technical Bulletin 1584. 7. Forbush, E. H. and Fernald, C. H. 1896. The Gypsy Moth. Wright & Potter, Boston. 8. Gerardi, M. H. and Grimm. J. K. 1979. The History, Biology, Damage, and Control of the Gypsy Moth, Porthetria dispar (L.). Associated University Presses, Cranberry, New Jersey. 9. An Article on History of Gypsy Moth, 1997, found at: http://www.ent.msu.edu/gypsyed/docs/history.html 10. Liebhold, A.M.; Halverson, J.A. & Elmes, G.A. (1992): Gypsy moth invasion in North America - a quantitative analysis. Journal of Biogeography 19(5): 513-520. 11. Gould, J.R.; Elkinton, J.S. & Wallner, W.E. (1990): Density-dependent suppression of experimentally created gypsy moth, Lymantria dispar (Lepidoptera, Lymantriidae), populations by natural enemies. Journal of Animal Ecology 59(1): 213-233. 12. Nyland, R. D. 2002 Silviculture: Concepts and Applications, Second Edition. Read More